<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title>作业2</title>
	
	<style>
		#top_context{
			height: 200px;
			background: #efefef;
			line-height: 200px;
			text-align: center;
		}
		#sticky{
			height: 20px;
			background: #000000;
			color: aliceblue;
			line-height: 20px;
			text-align: center;
		}
		#main_context{
					}
	</style>
	</head>
	<body>
		<div id="top_context">顶部内容区域</div>
		<div id="sticky">我是吸顶元素</div>
		<div id="main_context">Lorem ipsum dolor, sit amet consectetur adipisicing elit. Illum id velit consequatur harum quod reiciendis ipsam quia quo vel numquam nesciunt, explicabo voluptate omnis, itaque, ea dignissimos ipsa inventore aut?Lorem ipsum dolor, sit amet consectetur adipisicing elit. Tenetur minima similique atque doloremque nihil deleniti corrupti, eum rerum! Numquam quae facilis ipsa repellat qui sequi repellendus fuga eum inventore eligendi. Lorem ipsum dolor sit amet consectetur adipisicing elit. Exercitationem adipisci sint eum repellendus, tempore voluptates accusantium recusandae iure deserunt aperiam quisquam sit quasi sapiente obcaecati? Facilis maxime adipisci cupiditate earum.</div>
	</body>
</html>